As mobile usage continues to increase, the strategy of putting some features only on desktop web and others only on mobile web will become a worse and worse user experience; users will expect things to be consistently available on mobile.
We should aim for workflow equivalence (not necessarily exact 1:1 feature equivalence) where a platform blocker does not prevent something from working in one or the other place. In many cases we can ship the same JS/CSS modules and make sure they work on both mobile and desktop skins/layouts, though some cases will still require some target-specific adjustments.
This doesn't necessarily mean always running the same code or using the same skin, though when suitable it's a good practice. (cf "responsive" and "mobile first" buzzwords :)